The present invention relates generally to locomotive brake control and more specifically to an electronically controlled locomotive brake control.
For those countries under the auspices of the American Association of Railroads ("AAR") use a 26C brake valve and a 26F control valve for the locomotive brakes. The 26C brake valve includes an automatic brake handle for controlling the train brakes and an independent brake handle for independently controlling the locomotive brakes. The 26F control valve is responsive to the brake signals to operate the locomotive brakes. The 26C brake valve has a release/charge position, service position, suppression position, handle off position and an emergency position. In the release/charge position, the brake pipe is charged from a main reservoir. This not only charges the brake pipe, but causes release by increasing the pressure in the brake pipe. For very long trains, initially, the front end must be overcharged to assure release in the other end of the train. In AAR trains, emergency vent valves are distributed throughout the train to sense emergency conditions, namely an emergency drop in pressure in the brake pipe, to initiate emergency braking throughout the train. Also, the brake control valve in each of the cars can accelerate the release by locally applying pressure from a chamber in the valve to the brake pipe. This accelerates the transmittal of the release throughout the brake pipe. This local charging of the brake pipe for quick release is not at a sufficiently high rate as to prevent a break-in-two emergency brake application.
In some non-AAR countries or UIC countries, the brake control valves in the cars do not have the capability of locally dumping pressure into the brake pipe to locally increase the brake pipe pressure and therefore accelerate release. Thus, the locomotive brake controller has two positions for release or charging. It has a release position and a running position. In the release position, a substantially greater flow of pressure is provided to the brake pipe to give it a head start in charging back to the desired release brake pipe pressure. This is followed by placing the brake controller into a running position to allow a slower charging of the brake pipe to continue charging and release. The second rate will allow a break-in-two emergency brake application while the first rate will not.
The automatic brake control valve known as an H-6-L has a release, running, holding, lap, service and emergency positions. In the release position, a large and direct passage from the main reservoir to the brake pipe is provided. This quickly begins the charging of the brake pipe. To ensure release, the brake pipe is initially overcharged by the operator. If the handle is allowed to remain in this position for any length of time, the brake system would be charged to the main reservoir pressure. To avoid this, the handle is placed in the running position. A small port discharges main reservoir air to the atmosphere in the release position as sufficient noise to attract attention to the handle being in release.
In the running position, a large passage at the brake valve connects the feed valve pipe to the brake pipe. Thus, the brake pipe is charged under the feed valve control and cannot attain a pressure above that for which the feed valve is adjusted. The equalization reservoir charges uniformly with the brake pipe, keeping the pressure on the two sides of the equalization piston balanced. The two separate restrictions for the release position and the running position are basically mechanically in parallel to the brake pipe. To adjust these two orifices, the brake control valve must be disassembled and reconstructed.
The conversion of the 26C and the 26F to electronic or electropneumatic has progressed in AAR. A typical example is the CCBI and CCBII available from the New York Air Brake Corporation. The handle positions of the brake valve are electronically determined and used in electronic controls of the electropneumatic and pneumatic valves to duplicate the functions of the 26C and the 26F. There is a need for similar conversion in other countries that are not AAR, and especially in countries which include trains with older valve structures at the cars. Thus, there is a need to duplicate release, running and overcharging using electronic and electropneumatic controls of the release, running and brake pipe control at the electropneumatic brake controller.
The electropneumatic brake controller of the present invention includes a main reservoir, a pneumatic brake pipe relay first and second restrictions connected in series with the main reservoir, the brake pipe relay and brake pipe and a first electropneumatic valve connected in parallel to the second restriction. The second restriction is smaller than the first restriction. The first electropneumatic valve is responsive to an electric release signal to cut out the second restriction. When the two restrictions are in series, this is the running mode whereas when the second restriction is cut out, this is the release mode. The low running charging rate on the brake pipe allows the brake valves on the individual car to operate as if the original brake control valves were being used.
The controller includes manifolds to which is mounted the brake pipe relay, the first and second restrictions and the first electrical pneumatic valve. At least one, if not both restrictions are replaceable on the manifold. This allows replacement of the restrictions without mechanical reconstruction of the brake valve or the brake controller. The combination of the series connected first and second restriction has a flow rate sufficiently low to allow a break-in-two emergency brake application.
The first electropneumatic valve has an input connected to exhaust and a second input connected to a source of pressure. A pilot valve having a first input and output connecting the pilot valve in parallel to the second restriction and also includes a pilot input connected to the output of the first electropneumatic valve. The first pneumatic valve is biased to connect its output to exhaust when not activated and the pilot valve is biased to disconnect its first input and output when activated. Thus, for non-activation or failure of the electronics, the first and second restrictions are in series and thus, are always in the running mode with no ability to go to the release mode.
An equalization reservoir and a second electropneumatic valve controlling the pressure in the equalization reservoir are also provided. The brake pipe relay is responsive to the pressure difference between the brake pipe and the equalization reservoir. The second electropneumatic valve charges the equalization reservoir from the main reservoir during release. An operator control provides electric brake signals and a control unit generates the electric release signal in response to a brake control signal from the operator control.
The control unit also produces an overcharge condition in the brake pipe. The control unit through control of equalization reservoir and the restriction overcharges the brake pipe to a predetermined overcharged value. Once initiated, the control unit completes the overcharge in response to release or run brake control signals. The overcharge cycle is terminated in response to a service brake control signal. Once the overcharge value has been reached, the control unit maintains the overcharge value for a fixed period of time. After the fixed period of time, the control unit bleeds the brake pipe using the equalization reservoir control at a bleeding rate to a release pressure value. The control unit controls the brake pipe reduction in response to the service brake control signal from the brake pipe pressure at the charge and termination.
The overcharging cycle includes charging the brake pipe at a first rate to an overcharged value, holding the brake pipe at the overcharge value fixed period of time, and finally after the fixed period of time, bleeding the brake pipe at a bleeding rate to release pressure value. The charging, holding and bleeding cycle is continued once initiated in response to the release brake control signal. This cycle is terminated in response to service brake control signal. The reduction of the brake pipe pressure in response to a service brake control signal is from the brake pipe pressure at cycle termination.